[kiririn]

Concussion is a trial by fire of discovering what is truly not taking up mental energy. In the acute phase you go from having 16+ hours of it per day to 10 minutes. The answer is pretty much just staring at a blank wall. Anything else is costly to a degree

[plonk]

I had a mild one that put me out of work for a week. I wonder if it's really a lack of energy, or just the body deterring you from any activity by pretending to be tired, so the brain can heal faster.

[kradeelav]

Agreed - surgeries too. Between waiting for the anesthesia to work itself out and the body recovering from the shock of it, it can be a wallop to the energy reserves. Recently slept like 20 hours a day for a day or two after a comparatively mild one.